Obstruction of the gastrointestinal (GI) tract can be due to a wide range of causes with many similarities in clinical presentation. Abdominal pain, early satiety or anorexia, and vomiting are common, with abdominal distention being more common with lower tract blockage. Nonbilious emesis is seen in conditions that occur proximal to the sphincter of Oddi or early in the course of abnormalities occurring more distally. Conversely, bilious emesis is seen when obstruction or dysfunction occurs distal to the duodenum.

Obstruction can result from extrinsic compression, intrinsic blockage, or functional abnormalities leading to dysmotility, as detailed in Table 154-1. This chapter focuses on three of the more common causes of GI tract obstruction in children: pyloric stenosis, malrotation with and without volvulus, and intussusception.

Infantile hypertrophic pyloric stenosis (IHPS) is one of the most common surgically correctable causes of vomiting in infants. The incidence is about 1 in 250 to 500 with a 4:1 male preponderance; it is seen commonly in white and Hispanic infants and is rare in African, Indian, and Asian infants.^1,2 The familial incidence of pyloric stenosis is remarkable: the highest incidence of pyloric stenosis occurs in the male children of mothers who had pyloric stenosis, and there is a 15-fold increase in siblings of affected patients.^3,4 Traditional teaching has been that it is more common in firstborn males. The incidence of IHPS seems to be decreasing and seasonal variation has been recognized with the most common occurrences in the summer.⁵

Pyloric stenosis results from hypertrophy of the pylorus muscle with associated abnormalities in innervation and obstruction of the lumen with redundant mucosa. Although infectious causes have been speculated,⁶ the cause of the hypertrophy is unclear. Early exposure to erythromycin has also been considered a factor in the development of this condition.^7,8

CLINICAL PRESENTATION

Most infants with pyloric stenosis present between the ages of 3 and 8 weeks with progressive nonbilious emesis in large quantities, often forceful (“projectile”), after every feeding. The infant usually remains eager to feed, and recognition of the condition typically occurs before the infant experiences severe dehydration. However, if not diagnosed early, severe hypochloremic dehydration with metabolic alkalosis and growth failure will develop. With severe metabolic alkalosis the infant may present with apnea. Physical examination findings are often normal, but gastric distention, visible peristaltic waves, and a palpable “olive” (the hypertrophied pylorus) may be found. The “olive” is located in the lateral margin of the right rectus muscle just below the liver edge.

DIFFERENTIAL DIAGNOSIS

The differential diagnosis often includes gastroesophageal reflux, gastroenteritis, allergy, and other causes of proximal intestinal obstruction such as malrotation and volvulus.

DIAGNOSTIC EVALUATION

The hypertrophied pylorus may be apparent on either ultrasound or upper GI series. Ultrasound is much preferred because of the lack of radiation exposure with this testing. Ultrasound is considered positive if the pyloric channel is longer than approximately 14 to 16 mm with muscular thickness greater than 3.5 to 4 mm (Figure 154-1). Upper GI series, though it exposes the patient to radiation, can show the “string sign,” a thin line of barium visible as it passes through a thickened and elongated pylorus as well as compression of the gastric antrum and evidence of delayed gastric emptying.

Serum chemistry studies reveal hypochloremic metabolic alkalosis when the emesis has been prolonged, but evidence of metabolic acidosis may also be seen when the dehydration is pronounced.

MANAGEMENT

Although definitive treatment of pyloric stenosis is surgical, the initial management of pyloric stenosis focuses on correction of the dehydration, electrolyte disturbances, and acid-base abnormalities often present at the time of diagnosis. The mainstay of rehydration is intravenous (IV) fluids, initially with the administration of normal saline (20 mL/kg) followed by dextrose-containing maintenance fluids (e.g. 5% dextrose D5/0.45% saline). Serum potassium levels are often normal but total body potassium is depleted because of gastric losses, alkalosis, and secondary aldosterone effects. Therefore prompt supplementation of maintenance IV fluid with potassium chloride (20 mEq/L) after the first void is recommended. Serial serum electrolyte values are obtained until normalized. If IV access is not attainable at first, small volumes of oral electrolyte solution (e.g. Pedialyte) may be tolerated and may sufficiently hydrate the infant to improve the chance of successfully placing a peripheral IV catheter. Central IV access may be necessary if vomiting persists and peripheral IV access is not successful. At times, gastric decompression with a nasogastric tube is indicated preoperatively though that is not standard.

Pyloric stenosis is corrected surgically with a Ramstedt pyloromyotomy after correction of fluid and electrolyte abnormalities. Though there remains debate about surgical approach, open and laparoscopic pyloromyotomy both have low complication rates and high success.⁹ Postoperatively, feeding may be restarted within 24 hours. Early refeeding with full-strength formula or breast milk (i.e. without an initial trial of clear oral electrolyte solution) has been demonstrated to be safe and cost effective and allow more prompt discharge home.¹⁰ Many patients experience some postoperative emesis, thought to be related to postoperative ileus or swelling of the incised portion of the pylorus, or both. Persistent vomiting would not be expected and warrants further investigation. Inadequate pyloromyotomy is rare; other considerations are gastritis, gastroesophageal reflux, or previously undiagnosed gastric or intestinal obstruction.

ADMISSION AND DISCHARGE CRITERIA

All patients with pyloric stenosis should be admitted to correct fluid and electrolyte abnormalities and prepare them for surgery.

The baby can be discharged once feeding well after surgery, often in 1 to 2 days.

CONSULTATION

Early surgical consultation is recommended for definitive surgical intervention.

SPECIAL CONSIDERATIONS

Prevention

Identification of patients with an increased risk for pyloric stenosis may lead to earlier recognition. Newborn exposure to erythromycin has been associated with an eightfold increased risk, if the exposure occurs before 13 days of life. Exposure to erythromycin after 13 days of life or exposure to non-macrolide antibiotics is not believed to be associated with increased risk.⁸ Prenatal exposure to macrolides is not thought to increase the risk of pyloric stenosis.¹¹ Breastfed babies may have a lower rate of pyloric stenosis than bottle-fed babies.¹²

Malrotation results from failure of the intestine to rotate and fix normally during the first trimester of gestation. The midgut (distal duodenum to the transverse colon) extends into the umbilical cord during development and then rotates as it reenters the abdominal cavity. The distal third of the duodenum moves to the left of midline at the ligament of Treitz, whereas the cecum eventually situates itself in the right lower quadrant. At least six different anatomic positions are described as malrotation. Malrotation is reported to occur in up to 1 in 500 births, although the true incidence is uncertain because it can be asymptomatic. The incidence of malrotation is higher in children with other congenital anomalies, especially anomalies of the GI tract.¹³

Volvulus is the term used when twisting the intestines causes GI tract obstruction and ischemia (Figure 154-2). It is usually associated with malrotation, although adhesions or other pathology can lead to volvulus in a normally rotated GI tract. Most common is midgut volvulus, but gastric or cecal volvulus can occur and may also be associated with intestinal malrotation. Bowel wall ischemia leads to infarction or perforation, or both, which are life-threatening.

CLINICAL PRESENTATION